android - doInBackground() 错误

Question

我正在尝试从代码中的 5 个 URL 中获取值:

 new JsonTask().execute(urlPosts, urlPhotos, urlComments, urlComments, urlAlbums, urlUsers);

但是，我被困在这门课上了:

protected JSONObject[] doInBackground(String... params) {

        URLConnection urlConnection = null;
        BufferedReader bufferedReader = null;
        JSONObject[] jsonObjects = new JSONObject[4];

        jsonObjects[0] = getPosts();
        jsonObjects[1] = getPhotos();
        jsonObjects[2] = getComments();
        jsonObjects[3] = getAlbums();
        jsonObjects[4] = getUsers();

        return jsonObjects;
    }

错误:

E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1
              Process: com.example.marcellosouza.saberproject, PID: 12105
              java.lang.RuntimeException: An error occurred while executing doInBackground()
                  at android.os.AsyncTask$3.done(AsyncTask.java:309)
                  at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:354)
                  at java.util.concurrent.FutureTask.setException(FutureTask.java:223)
                  at java.util.concurrent.FutureTask.run(FutureTask.java:242)
                  at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
                  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
                  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
                  at java.lang.Thread.run(Thread.java:818)
               Caused by: java.lang.ArrayIndexOutOfBoundsException: length=4; index=4
                  at com.example.marcellosouza.saberproject.view.activity.MainPageBlogActivity$JsonTask.doInBackground(MainPageBlogActivity.java:102)
                  at com.example.marcellosouza.saberproject.view.activity.MainPageBlogActivity$JsonTask.doInBackground(MainPageBlogActivity.java:80)
                  at android.os.AsyncTask$2.call(AsyncTask.java:295)
                  at java.util.concurrent.FutureTask.run(FutureTask.java:237)
                  at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234) 
                  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113) 
                  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588) 
                  at java.lang.Thread.run(Thread.java:818) 

为什么会出现此错误？我该如何解决？谢谢。

Answer 1

Why am i getting this error?

你会清楚地知道为什么 - 只需仔细阅读整个堆栈跟踪:

Caused by: java.lang.ArrayIndexOutOfBoundsException: length=4; index=4

它甚至告诉您您的数组大小为 4 个元素(长度 = 4)，但您正试图超出它 -> index=4。由于数组索引从 0 开始，因此 4 表示第 5 个元素，因此崩溃。

然后堆栈跟踪会告诉您错误代码的位置:

com.example.marcellosouza.saberproject.view.activity.MainPageBlogActivity $JsonTask.doInBackground(MainPageBlogActivity.java:102)

你做错的是 - 你声明了 4 元素数组:

    JSONObject[] jsonObjects = new JSONObject[4];

但稍后您尝试在其中填充 5:

    jsonObjects[0] = getPosts();
    jsonObjects[1] = getPhotos();
    jsonObjects[2] = getComments();
    jsonObjects[3] = getAlbums();
    jsonObjects[4] = getUsers();

那是行不通的。修复 jsonObjects 创建或使用即 ArrayList 以避免固定大小的数组。